We have ways of making them oil tight, tho it does take some effort and investigation. The biggest improvement comes from using low expansion pistons and chrome compression rings. When properly seated, this combo results in more power, longer top end life and much less oil consumption. There is little blowby and less crankcase pressure, or in some situations, slightly negative crankcase pressure. The crankcase pressure reduction gets rid of a whole host of little leaks/seeps.
The other big improvement is to add a valve seal to the intake valves.
These two changes combined can get you 1600 miles down the road on an 8 oz. cup of oil, a far cry from the factory spec of 160 fluid oz per 1500 miles!
The engine stays clean, the rear wheel is not wet with oil anymore, a big improvement.
Glen
